This application claims priority from Korean Patent Application No. 10-2005-0000383, filed on Jan. 4, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field Of The Invention
The present invention relates to a hard disk drive (HDD) and, more particularly, to a structure and method for reducing an impedance-discontinuity in a flexible printed circuit of an HDD.
2. Description Of The Related Art
Hard disk drives (HDDs), which are auxiliary information storage devices for computers, read data stored in a disk or write data to the disk using a read/write head.
FIG. 1 is a top plan view of a conventional HDD. Here, an HDD employing a contact start stop (CSS) type head parking system will now be explained.
Referring to FIG. 1, the HDD includes a magnetic disk (hard disk) 20 acting as a data recording medium, a spindle motor 30 installed on a base member 10 and rotating the disk 20, an actuator arm 40 having a read/write head 41 for writing data on the disk 20 and reading data written to the disk 20, a flexible printed circuit unit 60 transferring data to a printed circuit board (PCB) that is installed under the base member 10, and a flexible printed circuit 70 interconnected from the flexible printed circuit unit 60 to the actuator arm 40.
The actuator arm 40 includes a swing arm 46 that can pivot about a pivot 47 installed on the base member 10. A suspension 44 is installed at an end of the swing arm 46 to elastically bias a slider 42 on which the read/write head 41 is mounted toward a surface of the disk 20.
The actuator arm 40 is rotated by a voice coil motor (VCM) 50. The VCM 50 includes a VCM coil 56 coupled to the other end of the swing arm 46. Magnets (not shown) are disposed over and under the VCM coil 56 to face the VCM coil 56.
During write and read operations of the conventional HDD having this structure, a lifting force induced by the rotation of the disk 20 and an elastic force of the suspension 44 are applied to the slider 42 on which the read/write head 41 is mounted. Accordingly, the slider 42 is kept floating at a predetermined height where the lifting force and the elastic force are balanced. As a result, the read/write head 41 mounted on the slider 42 writes or reads data on the disk 20 while being spaced a predetermined distance from the rotating disk 20.
An impedance-discontinuity occurs in the flexible printed circuit of the conventional HDD, which will now be explained with reference to FIGS. 2 and 3.
FIG. 2 is a vertical sectional view of the flexible printed circuit unit shown in FIG. 1. FIG. 3 is a vertical sectional view of the flexible printed circuit disposed between a bracket and the actuator arm shown in FIG. 1.
Referring to FIGS. 2 and 3, the flexible printed circuit unit 60 includes a bracket 63 and a flexible printed circuit 64 disposed over the bracket 63. The flexible printed circuit 64 includes an insulator 62 and various circuits 61 formed on the insulator 62. The flexible printed circuit 70 disposed between the actuator arm 40 and the bracket 63 includes an insulator 72 and various circuits 71 formed on the insulator 72. Here, although the flexible printed circuits 64 and 70 are integrally formed with each other, they are given different reference numerals because their positions are different, for a convenient explanation.
In general, the base member 10 is made of metal. Various metal parts including the bracket 63 are attached to the base member 10. Accordingly, since the flexible printed circuit 64 disposed over the bracket 63 is in close contact with the base member 10 and the metal parts attached to the base member 10, the flexible printed circuit 64 significantly affects the base member 10 and the metal parts attached to the base member 10.
However, both ends of the flexible printed circuit 70 are respectively installed at the actuator arm 40 and the bracket 63, such that the flexible printed circuit 70 interposed between the actuator arm 40 and the bracket 63 is located in a space above the base member 10. Accordingly, as compared with the flexible printed circuit 64 disposed over the bracket 63, the flexible printed circuit 70 has less of an affect on the base member 10 and the metal parts attached to the base member 10.
Consequently, although the flexible printed circuits 64 and 70 are integrally formed with each other, an electromagnetic field formed around the flexible printed circuit 64 is different from an electromagnetic field formed around the flexible printed circuit 70, and thus impedances of the flexible printed circuits 64 and 70 are different from each other. In particular, the impedance at a point where the flexible printed circuit 64 is connected to the bracket 63 is considerably different from the impedance at a point where the flexible printed circuit 70 is connected to the actuator arm 40. If the impedance-discontinuity occurs between the flexible printed circuits 64 and 70, electric signals transmitted through the flexible printed circuits 64 and 70 are delayed or lost, thereby resulting in malfunction of the HDD or electromagnetic interference (EMI) with the HDD.